1. Field of the Invention
The present invention relates to a nitride semiconductor light emitting device capable of emitting light in blue to ultraviolet regions and, more specifically, to a structure of a nitride semiconductor light emitting device using an Si substrate.
2. Description of the Background Art
Conventionally, it has been known that a nitride semiconductor light emitting device may be used as a blue light emitting device. Recently, blue light emitting diodes and violet semiconductor laser have been studied. FIG. 11 shows a schematic structure of a nitride semiconductor light emitting device disclosed in Japanese Patent Laying-Open No. 2001-7395. The nitride semiconductor light emitting device has such a structure in that on an Si substrate 100, a lower clad layer 200 of an n type nitride semiconductor, a light emitting layer 300 and an upper clad layer 400 of a p type nitride semiconductor are stacked in this order, with a p type ohmic electrode 500 formed on upper clad layer 400 and an n type ohmic electrode 600 formed on Si substrate 100.
Consider the structure of the nitride semiconductor light emitting device disclosed in Japanese Patent Laying-Open No. 2001-7395 in which a n type nitride semiconductor layer and a p type nitride semiconductor layer are stacked successively on Si substrate. When a current blocking structure or a current constricting structure is to be formed in order to improve light emitting efficiency in the light emitting device, it is necessary to form an insulating film or a current blocking film, on a p type nitride semiconductor layer, which is doped with Mg (magnesium), thin and has high resistivity.
Therefore, conventionally, the p type nitride semiconductor layer is damaged when the insulating film or the current blocking film is formed, resulting in crystal defects generated in the p type nitride semiconductor layer, which crystal defects capture Mg. Further, in most cases, the insulating film contains oxygen, and the oxygen introduced to the surface and to the inside of the p type nitride semiconductor layer oxidizes Mg. Therefore, concentration of Mg as the impurity in the p type nitride semiconductor layer decreases, further increasing the resistivity and deteriorating characteristics of the light emitting device.
Further, when the insulating film or the current blocking film is to be formed on the p type nitride semiconductor layer as described above, the step of fabrication of such a film is necessary.
Because of these problems, it has been difficult to form a current blocking structure or a current constricting structure in the light emitting device.
In view of the foregoing, an object of the present invention is to fabricate a current blocking structure or a current constricting structure easily in a light emitting device, and to fabricate a highly reliable nitride light emitting device.
The above described object can be attained by the nitride semiconductor light emitting device in accordance with the present invention that includes a p type nitride semiconductor layer, a light emitting layer and an n type nitride semiconductor layer stacked on an Si (silicon) substrate in this order from the Si substrate, wherein the Si substrate is partially removed to expose a part of the p type nitride semiconductor layer, and on the exposed region of p type nitride semiconductor layer, a p type electrode is formed.
In the nitride semiconductor light emitting device of the present invention, an n type pad electrode may be formed at a corner on the surface of the n type nitride semiconductor layer.
In the nitride semiconductor light emitting device of the present invention, the p type nitride semiconductor layer may include a region having high dopant concentration and a region having low dopant concentration.
In the nitride semiconductor light emitting device of the present invention, the backside of the Si substrate opposite to the surface having the stack formed thereon is partially removed to have a recessed or protruded shape, and the surface of the p type nitride semiconductor layer may be exposed at the removed region.
In the nitride semiconductor light emitting device of the present invention, when the back side of Si substrate opposite to the surface having the stack formed thereon is partially removed to have a recessed shape, a reflective film is formed at the recessed portion.
Further, in the nitride semiconductor light emitting device of the present invention, when the backside of the Si substrate opposite to the surface having the stack formed thereon is partially removed to have a protruded shape, the n type nitride semiconductor layer may be formed to have a protruded shape. Further, in this case, an n type pad electrode, or an n type pad electrode and an n type light emitting electrode may be formed at the top of the protruding portion of n type nitride semiconductor layer.
In the nitride semiconductor light emitting device of the present invention, that region of the p type nitride semiconductor layer which is positioned on the region where the Si substrate is removed may have higher dopant concentration than other regions of the p type nitride semiconductor layer.
In the nitride semiconductor light emitting device of the present invention, the Si substrate is non-conductive, and it may be non-light transmitting.
Further, the present invention provides a method of manufacturing a nitride semiconductor light emitting device, including the steps of stacking a p type nitride semiconductor layer, a light emitting layer and an n type nitride semiconductor layer in this order on an Si substrate to form a stacked body; removing a part of the Si substrate; exposing the surface of the p type nitride semiconductor layer from the portion where the Si substrate is removed; heat-treating the stacked body with part of the Si substrate removed; and forming a p type electrode on the exposed surface of the p type nitride semiconductor layer.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.